Arnd Bergmann wrote at Wednesday, August 17, 2011 5:24 AM: > On Tuesday 16 August 2011, Stephen Warren wrote: > > One issue here: There isn't always a single gpio/pinmux parent; as a > > concrete example, the ALSA/ASoC driver for Tegra+WM8903 uses GPIOs both > > from Tegra itself, and from the WM8903 audio codec. > > > > I could imagine the same being true in basically any case where one > > device uses N GPIOs (e.g. SD controller with power, change-detect, > > and read-only GPIOs; some could easily come from the SoC and some > > from a GPIO expander). > > > > I'm not quite so sure that multiple parents would be useful for pinmux, > > but I wouldn't say that it was impossible... > > Hmm, how common do you think the example is? > > It it's just a very rare case, we can still special-case it by > introducing fake subdevices for the Tegra+WM8903 driver, each of > which has only one gpio-parent. This is ugly but keeps the special > case to the rare devices. > > If we can expect more than a handful of these, we probably need > a better design for the binding, which will cause a burden for > all drivers. It looks like DT already supports the generic case for GPIO; each GPIO reference is of the form: <&gpio 69 0> and so each GPIO has a "parent" specified, and hence can come from a different controller. For drivers, this is all completely hidden by of_get_gpio(). I imagine we'd just use the same pattern for pinmux. This would both support the general case, and end up being consistent with how GPIOs already work, so this seems like a win both ways. -- nvpublic -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
